1. Field of the Invention
This invention relates to an improved device in the area of fans, blowers, propellers, screws, and the like. In particular, this invention relates to a device having a rotating shaft wherein compressed air is generated and pushed forward parallel to the longitudinal axis of the shaft.
2. Description of the Prior Art
Devices such as fans and blowers are well known for use in generating an air stream. Also well known are devices that are powered by wind and by streams of water; for example, windmills, water wheels, and turbines. Disadvantages of the above devices consist of unwanted diffusion of air hitting a fan, the need for a special cover for the blower, and loss of operating efficiency arising from the alignment of blades in a fan.
A fan typically comprises a rotatable shaft onto which are mounted a number of blades spaced apart from each other. When the shaft rotates, the blades turn and push a mass of air in the direction of the longitudinal axis of the shaft. The amount of air moved in a period of time is proportional to the angle at which each blade is mounted with respect to the longitudinal axis of the shaft, and the shaft's speed of rotation. For example, the closer the face of the blade is to an angle perpendicular to the longitudinal axis of the shaft, the smaller is the amount of air deflected by the blade as the shaft rotates. A decrease in the blade angle with respect to the shaft means that the blade pushes a greater mass of air as the shaft rotates. Air hitting a moving blade is deflected from the blade at an angle approximately similar to the incident angle of air hitting the blade. Air hitting the fan blade at different angles is deflected in turn from the blade at different angles; some of the air deflected from the moving blade tends to be diffused, an undesirable characteristic for many applications.
One can cause a decrease in the diffusion of air by the use of curved blades on the fan, a portion of which is shown in FIG. 1. In order to help understand the characteristics of a curved-blade fan, one can visualize an imaginary line between the center of the shaft 2 to which the blade 3 is attached, and the outermost tip 4 of blade 3 farthest from the shaft 2. Typically the blade 3 is attached to the shaft 2 at a point 5 that lies along the imaginary line 1. In some fans, the radial center 6 of the curved blade 3 is at a point away from the imaginary line 1, so that some of the air hitting the blade 3 is diffused. For example, as the shaft 2 turns in a counter clockwise direction, air 7 hitting the upper half of the curved blade 3, such as at point 8, is deflected toward the shaft 2. However, air 9 hitting the lower half of the curved blade 3, such as at point 10, is deflected away from shaft 2 and becomes diffused.
In other fans, the radial center 16 of the curved blade 13 is on the imaginary line 11 from the center of the shaft 12 to the outermost edge 14 of the blade 13, as indicated in FIG. 2. The curvature of such a blade 13 often approaches that of a half circle. Much of the air 17 hitting the curved blade 13, such as at point 18, is deflected inside the curvature toward the shaft 12, as the latter turns in a counter clockwise direction. However, some air 19 hitting the lower half of the curved blade 13, such as at point 20 is still deflected away from, rather than toward, the shaft 12. For maximum efficiency, it is desirable that the blade deflect most if not all of the air hitting it toward the shaft, and reduce, or eliminate, the quantity of diffused air, so that most or all of the air covered by the blade curvature moves in the direction desired. None of the prior-art fans are able to accomplish this objective.
Efficiency of a fan is increased when most or all of the air hitting the fan blades is used, the air moves in the direction desired after being deflected, and little or no air moving the direction of the fan manages to escape. Standing in front of a typical fan and looking in the direction of the longitudinal axis of its shaft, one sees space between the fan blades, as indicated in FIG. 3. Consequently, air at this space is not used until the blades move into the empty space, resulting in a waste of the available air in the vicinity of the fan. Furthermore, a new open air space appears after the blade moves away until the next blade moves into this space. Moreover, when this kind of fan is used as a windmill, some of the wind can escape through this space before the blades move into the space, resulting in a waste of the wind.
Another kind of fan has blades aligned so that a portion of the back of one blade overlaps a portion of the front of another blade, as shown in FIG. 4. The overlapping blades prevent the deflected air from moving in the direction desired. As the blades move, some of the air deflected by one blade hits the overlapping portion of the other blade, which causes a loss of concentration of deflected air. Thus a fan is needed that prevents the waste of the space due to a gap between the blades, while at the same time preventing loss of the deflected air due to blades overlapping one another.
A cover over the fan has been used in some prior-art devices to control the flow of air and decrease diffusion. Inlets in the cover allow air to be pulled in, usually by use of a rotating shaft on which are mounted a number of spaced scoops, cups, or blades. A narrow outlet is provided in the cover through which the moving scoops or blades push the air, which becomes a narrow air stream. For some applications, however, a cover to channel the air flow is either inconvenient, or expensive, or both.
Thus there is a need for a device with a rotating shaft that generates an air stream which moves forward parallel to the longitudinal axis of the shaft, that reduces the amount of diffused air, that increases the efficiency of operation by using all of the air, that does not allow air to escape nor rebound from one blade to another, and that eliminates the need for a special cover to control air flow.